Although the frequency of the output waveform varies with the input voltage, the PWM circuit exhibits a linear relationship between input voltage and output duty cycle

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• Article «Low-power PWM circuit is simple, inexpensive»
• Figure 1. In this PWM circuit, adjusting the input voltage, V_I, changes the emitter potentials of Q₁ and Q₂ and thus varies the charge and discharge currents of C₁ so that the duty cycle of the output varies in direct lin
• Figure 2. The changing voltage, V_C, across C₁ and the hysteresis, V_H, of IC_1A determine the duty cycle, T₁/(T₁ + T₂), of the output waveform. V_TU and V_TL are IC₁
• Figure 3. Although the frequency of the output waveform varies with the input voltage, the PWM circuit exhibits a linear relationship between input voltage and output duty cycle